In plural-component polyurea spray elastomer technology, it is usually necessary to govern the speed of reaction, for practical reasons. Generally, the slowing of polyurea systems is accomplished via the use of specialized diamines that can delay the onset of cure through a combination of steric and electronic factors. The diamines are typically low-molecular weight cyclic species and are commonly referred to as chain extenders by those skilled in the art of polyurea elastomer technology.
The current state of the art polyurea elastomer technology utilizes low-molecular weight secondary amine chain extenders to tailor the speed of polyurea spray elastomer systems. Presently, UNILINK® 4200 from UOP is the main chain extender employed to extend gel and tack-free times. This product is relatively high in cost at ˜$4.50–5.00/lb, and has proven cost prohibitive in some circumstances. An aliphatic version of UNILINK® 4200 is available from UOP under the tradename CLEARLINK® 1000, as well.